Are there any studies which attempt to use AI to guess the human emotion based on the brainwaves?
As per this site


  Researchers recorded the complex patterns of electrical activity generated by someone’s brain, as the subject listened to someone talking.
  By feeding those brainwave patterns into a computer, they were able to translate them back into actual words — the same words that the volunteer had been hearing.
  
  The scientists behind the work believe they can now go further and read the unspoken thoughts of people using electrodes placed against the brain.
  
  In the experiment, each patient listened to a recording of spoken words for five to ten minutes, while the net of electrodes placed under their skull monitored activity in a part of the brain involved in understanding speech called Wernicke’s area.
  
  In one experiment, volunteers looked at black-and-white photographs while the scanner monitored activity in part of the brain that handles vision called the primary visual cortex.
  A computer predicted accurately the image that the person was looking at purely from the pattern of brain activity.


So AI might be able to read our emotions as well in near future.

I found that google glasses can detect people's emotion via facial expression, voice tone e.t.c, (just like us), obviously not what they are thinking in their brain.